Lung involvement in rheumatoid arthritis, a prospective study

The prevalence of lung involvement in rheumatoid arthritis (RA) remains elusive. Therefore, we set up a multicentric prospective study to investigate the presence of interstitial lung disease (ILD), emphysema, bronchiolitis and nodules in early RA.

We recruited patients with RA and a disease duration from 1 to 10 years to screening. Patients underwent comprehensive respiratory evaluation consisting of an environmental questionnaire, high-resolution computed tomography (HRCT), pulmonary function tests (PFTs) and sampling for genetic analysis of common variants associated with RA-ILD. HRCT scans were centrally reviewed.

We included 258 RA patients, median age 56 years old, 71% female and 49% ex- or current smokers. We detected ILD, emphysema and >20% air trapping in 38 (15%), 51 (20%) and 89 (34%) patients, respectively. Older age, male sex, disease activity and lower diffusing capacity of the lung for carbon monoxide (D _LCO) were significantly associated with ILD; and older age, male sex, smoking status and lower D _LCO were associated with emphysema. No variables were associated with air trapping. Finally, we built stepwise logistic regression models for ILD and emphysema. Older age, higher Disease Activity Score-28, seropositivity for rheumatoid factor, lower D _LCO and MUC5B variant were predictors of ILD, whereas the number of pack-years smoking was predictive of emphysema.

Lung involvement affects a high proportion of early-stage RA patients, constrictive bronchiolitis being the most prevalent, followed by emphysema and ILD. Older age, uncontrolled disease, male sex and lower D _LCO were associated with both ILD and emphysema, suggesting that we should prioritise screening in these subpopulations.